(1) Field of the Invention
The present invention relates to an electromagnetic wave shielding material which can be seen through and has an electromagnetic wave shielding effect, and in which deformation such as warping or bending or generation of the internal strain is controlled and various resistance characteristics are excellent. More particularly, the present invention relates to an electromagnetic wave shielding material in which a light scattering property is given to the surface and which is excellent in the easy-to-see characteristic of an image on a Braun tube.
(2) Description of the Prior Art
With recent development of OA devices and other electronic devices, an electromagnetic wave shielding plate which has an electromagnetic wave shielding effect and can be seen through is desired for a CRT filter of an OA device or a peeping window of a shield chamber of an electronic device so as to prevent generation of a noise or prevent dilect influences of electromagnetic waves on the human body.
As the conventional electromagnetic shielding plate that can be seen through, there can be mentioned (1) a porous metal plate such as a punched metal plate, (2) an article formed by coating a transparent material with an electroconductive metal oxide or metal by vacuum evaporation deposition or the like, (3) an electroconductive synthetic fiber net and (4) a net of a metal such as stainless steel. The plate (1) is defective in that the shielding effect is reduced with the lapse of time by corrosion or the like, and the plate (2) is defective in that a sufficient shielding effect can hardly be obtained. The net (3) can be formed relatively easily, but the net is readily broken or corroded and cleaning for removing adherent dusts is difficult. The net (4) is defective in that a product comprising filaments having a fine diameter can hardly be obtained.
As another known electromagnetic wave shielding plate, there can be mentioned a product formed by interposing an electroconductive net between two transparent resin plates and integrating the assembly. However, the sharpness of the seen-through image is reduced by reflection of light rays on the surface of the transparent resin plate, and a reflected image is an eyesore. This defect is made more conspicuous by reduction of the transmittance of the transmitted light.